1. Field of Invention
The present invention relates to a liquid crystal device. More particularly, the present invention relates to an impulse driving apparatus and method thereof for liquid crystal devices.
2. Description of Related Art
Recently, the cathode ray tube (CRT, herein after) display devices are gradually being replaced by liquid crystal displays. The improvements of semiconductor technology enable liquid crystal displays to deliver many benefits including low power consumption, slim shape, light weight, high resolution, good color saturation, and long product life. Hence liquid crystal displays are widely used in electronic devices, such as display screens of portable computers or desktop computers, televisions (TVs), etc. Wherein, the quality of a liquid crystal device is the key factor for a good quality liquid crystal display.
Referring to FIG. 1, the block diagram of a conventional thin film transistor LCD is shown. Wherein, a data driver 110 drives a plurality of data lines 112˜118 to output data signals for driving pixels, a gate driver 130 drives a plurality of gate lines 132˜138 that are also known as scan lines, and a display area 120 includes a plurality of transistors 152˜168 and storage capacitors 181˜197.
The operation of a conventional liquid crystal display is described as follows. First, a gate line, e.g. gate line 132 is driven for turning on the transistors 152˜156 on the gate line 132. At the same time, pixel data signals for displaying are inputted through data lines 112˜118 to charge storage capacitors 181˜185. Then, the next gate line is driven, e.g. gate line 134, and the pixel data signals for displaying are inputted through data lines 112˜118 to charge storage capacitors 187˜191. Accordingly, storage capacitors 181˜197 in the display area 120 are charged in sequence for displaying a complete image.
The operations described above are perfect for displaying a static image. But an image dragging will occur to the dynamic image with a fast refresh speed while the voltage charged to storage capacitors can not be refreshed in time. In order to resolve the problem of image dragging when displaying dynamic images, the Samsung Electronics of Korea had proposed an impulse driving liquid crystal display by emulating CRT operations according to the Korea patent No. 2002-0066823, which is published on Aug. 21, 2002.
Referring to FIG. 2, an operating timing diagram of the impulse driving liquid crystal display proposed by Samsung Electronics is shown. Wherein, DATA is an image data on data line for driving pixels, STH is a start horizontal signal, TP is a load signal, CPV is a gate clock signal, and STV is a start vertical signal. In order to emulate the impulse display operations of a CRT, the image data DATA is outputted as the pixel data with a black data inserted in 1H cycle of the scan line, as shown in FIG. 2. Then a data driver receives and stores the image data on data lines and generates data signals for driving pixels according to the start horizontal signal STH and the load signal TP. Meanwhile, a gate driver generates scan signals for driving gate lines according to the gate clock signal CPV and the start vertical signal STV.
However, according to the timing diagram in FIG. 2, the aforementioned method requires double frequency for the start horizontal signal STH and the load signal TP compared to the operation of a conventional liquid crystal display and hence limiting the charging time for storage capacitors to only half of the original charging time or even less. Furthermore, additional line memories are required because pixel data and black data are transmitted alternately.